Java JScrollPane问题

我制作了一个带有滚动窗格的程序，但它不工作。请看源代码：

JInfoView.java

package view;
import javax.swing.*;
import java.util.*;
import java.awt.*;
public class JInfoView extends JPanel {
    private JButton button = new JButton("ADD");
    private JButton buttonDelete = new JButton("DEL");
    private JTextField input = new JTextField("Text", 5);
    private JLabel label = new JLabel("Test");
    public JInfoView() {
        this.setLayout(new FlowLayout());
        this.add(button);
        this.add(buttonDelete);
        this.add(input);
        this.add(label);
    }
}

JMainView.java

package view;
import java.awt.*;
import javax.swing.*;
import java.util.*;
import view.JInfoView;

public class JMainView extends JFrame {
    private JPanel mypanel = new JPanel(new GridLayout(0, 1, 30, 50));
    private JScrollPane scrollPane = new JScrollPane(mypanel);
    public JMainView() {
        super("Simple Example");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container container = this.getContentPane();
        container.setLayout(new FlowLayout());
        container.add(scrollPane);

        scrollPane.setVisible(true);
        scrollPane.setAutoscrolls(true); 

        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());       
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView()); 
        mypanel.add(new JInfoView());
    }

    public static void main(String[] args) {
        JMainView app = new JMainView();
        app.setVisible(true);
    }
}

我读过一篇教程，上面说：

//In a container that uses a BorderLayout:
textArea = new JTextArea(5, 30);
...
JScrollPane scrollPane = new JScrollPane(textArea);
...
setPreferredSize(new Dimension(450, 110));
...
add(scrollPane, BorderLayout.CENTER);

我也做了同样的步骤

private JPanel mypanel = new JPanel(new GridLayout(0, 1, 30, 50));
private JScrollPane scrollPane = new JScrollPane(mypanel);

然后添加滚动窗格：

container.add(scrollPane);

哪里有错误？ 编辑： 问题是滚动窗格不工作。我在mypanel中添加了许多JInfoView，

---

但是scroll不起作用。

您忘记添加

scrollPane。setPreferredSize

如下调用：

public class JMainView extends JFrame {
    private JPanel mypanel = new JPanel(new GridLayout(0, 1, 30, 50));
    private JScrollPane scrollPane = new JScrollPane(mypanel);
    public JMainView() {
        super("Simple Example");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container container = this.getContentPane();
        container.setLayout(new FlowLayout());
        container.add(scrollPane);

        scrollPane.setVisible(true);
        scrollPane.setAutoscrolls(true);
        scrollPane.setPreferredSize(new Dimension(300, 400)); //========== this was missed

        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        this.pack();
    }

    public static void main(String[] args) {
        JMainView app = new JMainView();
        app.setVisible(true);
    }
}

---

如果

JScrollPane

位于

BorderLayout

的

中心

，它似乎工作正常。例如

import javax.swing.*;
import java.util.*;
import java.awt.*;

import java.awt.*;
import javax.swing.*;
import java.util.*;

public class JMainView extends JFrame {
    private JPanel mypanel = new JPanel(new GridLayout(0, 1, 30, 50));
    private JScrollPane scrollPane = new JScrollPane(mypanel);
    public JMainView() {
        super("Simple Example");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container container = this.getContentPane();
        container.setLayout(new BorderLayout());
        container.add(scrollPane);

        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
    }

    public static void main(String[] args) {
        JMainView app = new JMainView();
        // important!
        app.pack();
        // show the scroll bars by compressing the GUI height
        app.setSize(
            (int)app.getSize().getWidth()+30, 
            (int)app.getSize().getHeight()/2);
        app.setVisible(true);
    }
}

class JInfoView extends JPanel {
    private JButton button = new JButton("ADD");
    private JButton buttonDelete = new JButton("DEL");
    private JTextField input = new JTextField("Text", 5);
    private JLabel label = new JLabel("Test");
    public JInfoView() {
        this.setLayout(new FlowLayout());
        this.add(button);
        this.add(buttonDelete);
        this.add(input);
        this.add(label);
    }
}

---

你没有描述什么不起作用。不要让我们复制你的代码并测试它，然后看到错误。请描述@Mat:what不起作用的问题？抱歉，我刚刚编辑了这个问题。@maximus和new'JPanel（new GridLayout（0，1，30，50））的定义；'与添加的“mypanel.add（new JInfoView（））；”的编号不对应mKorbel为什么不呢？新的GridLayout（0、1、30、50）意味着可以有任意数量的行，而只有一列。是吗？你的意思是吗？@denisk你的回答是不是意味着，在向mypanel添加新元素时，scrollpane的首选大小会发生变化？@maximus：我不知道它是否会发生变化（我想不会），只需指定Calling

setPreferredSize（Dimension）

是不可取的（绝大多数情况下）在这种情况下也没有必要。